SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6d5f281165ee39b52a0ca4376ed2d926c364f82c8f88f25542774fe70872414' 
  AND token = 'txTjO+Fp5Ii04KAILNFfvS/sYsgTPQVgCLITgzFrbHM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}